Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
It is known that a product such as grain can be monitored by an optical methodology to determine, for example, the percentage of moisture present in the grain. This is a key economic factor for the purpose of quality assessment and determination of any process steps that might be required such as drying of the grain during initial storage. This field is one to which embodiments of the invention can be applied. Portable moisture meters suitable for in-field use are known but there is considerable difficulty in aligning the output from such moisture meters with laboratory type equipment using sophisticated and expensive near infrared technology which has been developed for use at grain receival points.
Relatively expensive equipment is known for use in laboratory and receival conditions to measure the moisture in grain with sufficient accuracy for trading.
It is known that the amount of electromagnetic radiation, and more usually visible light or near IR radiation, absorbed at a particular typically narrow range of wavelengths is proportional to the concentration of a light absorbing component or species and the path length of the light through the sample. Accordingly, by illuminating a sample with light an analysis of the transmitted light through the sample at appropriate wavelengths can be affected to determine the concentration of the relevant chemical component such as water. Physical calibration with a range of samples with known properties is required. Calibration precisely relates the amount of the light absorbed with the concentration of the absorbing species at the relevant range of wavelengths. The range of wavelengths more commonly used is selected from the near infrared, the mid infra-red or the visible portion of the electromagnetic spectrum.
One example applicable to the task of measuring moisture in grain is described in U.S. Pat. No. 6,031,608 (Van Bargen and Norris) which describes an instrument operating at near infrared frequencies (“NIR”) which are about 780 nm to about 2,500 nm. The instrument uses a spherical diffraction grating from which light is reflected over a spread of frequencies. The diffraction grating causes the incident light to be reflected at different angles depending on the wavelength of the incident light. By positioning an optical detector at the appropriate position, the intensity of light at a specific wavelength can be measured. The measurements can then be used to develop the relationship between concentration of absorbing species such as moisture and light absorbance.
In U.S. Pat. No. 6,031,608 the grating is moved in an oscillatory manner so that a selected very narrow bandwidth of light is incident on a sample from which there is reflection to a detector. At any instant the amplitude of light on the detector is measured with respect to the incident frequency. This gives a measure of the degree of absorption of the illuminated sample and thus determines a characteristic of the sample. For example, the sample may be a specimen of grain in which the moisture content is to be determined. It is well known that an absorption peak in the spectrum of grain related to water is spread around about 965 nm. However frequencies either side of this centre frequency must also be examined in order to determine, in this case, the moisture content. This apparatus is complex with its moving parts and most significantly is a laboratory type instrument requiring meticulous calibration so that the raw data for a signal (the strength recorded at different frequencies) can be processed in accordance with a relationship governed by the particular piece of equipment to determine moisture content. U.S. Pat. No. 6,031,608 deals with a particular development to offset the axis of oscillation from a tangent to the spherical diffraction grating and thus is aimed at solving a problem particular to complex machines in which oscillation occurs to scan through the frequency spectrum.
Other examples in the field are:
U.S. Pat. No.Inventor5,589,717Chiu Chau5,880,834Michael P Chrisp4,850,706Thomas Mikes4,997,280Karl Norris5,132,538Karl Norris
In addition, PCT applications WO 02/40968 and WO 02/40967 have disclosures relating to grain monitoring by use of light.
The abovementioned patent specifications can be located by appropriate searching but recognition of these documents is not to be taken as admission that the content is actually known generally or forms part of the general knowledge to persons ordinarily skilled in the field.
Particularly for applications in the food and beverage area spectrographic monitoring techniques are widely known. A leading text is “Practical NIR Spectroscopy” (Osborne et al) published by Longman Scientific and Technical. Page 29 of the 2nd Edition demonstrates that various components have observed characterising absorption bands at NIR frequencies. By using the reciprocal of reflectance or transmittance in presentations and especially graphic presentations, then the absorption is characterised by a “peak” centred on a main frequency.
The present invention is directed to new and alternative approaches to spectroscopy especially applicable to the agricultural, and beverage industries but not necessarily confined thereto. One important application of some of the preferred embodiments of the invention that will be described in detail is the monitoring of moisture in grain. However, the equipment and principles described herein are equally applicable to monitoring other characteristics, such as protein in grain, particularly in the NIR portion of the spectrum.
A critical limitation pointed out by the present inventors is that equipment available on the market is essentially laboratory scale equipment which is capable of highly accurate performance but is essentially not suitable for field use. Furthermore, and most importantly, it is relatively expensive equipment particularly because of the expensive and careful alignment steps needed for each and every instrument so that the output data from all the instruments is consistent. That is, considerable effort and expense is expended in ensuring that all the instruments will provide consistent results for a given sample.
The inventors have observed an important un-met need for equipment which can be robust, relatively inexpensive, easily manufactured and suitable for field use, for example, by farmers who need to quickly and with reasonable accuracy determine characteristics such as protein and moisture content in grain prior to harvesting and shipment to a receiving station. If the grain has excessive moisture, it may be rejected at great economic loss to the farmer or if the moisture is somewhat high then the price will be downgraded.